Wide area and local network ID transmission for communication systems

ABSTRACT

The embodiments utilize OFDM symbols to communicate network IDs. The IDs are encoded into symbols utilizing the network IDs as seeds to scramble respective pilots that are then transmitted by utilizing the symbols. The pilots can be structured into a single OFDM symbol and/or multiple OFDM symbols. The single symbol structure for transmitting the network IDs is independent of the number of network ID bits and minimizes frequency offset and Doppler effects. The multiple symbol structure allows a much coarser timing accuracy to be employed at the expense of transmitting additional symbols. Several embodiments employ a search function to find possible network ID candidates from a transmitted symbol and a selection function to find an optimum candidate from a network ID candidate list.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/021,310, filed Dec. 22, 2004, which is incorporated by referencedherein in its entirety for all purposes.

BACKGROUND

I. Field

The embodiments relate generally to data communications, and moreparticularly to systems and methods for structuring network IDs intoOFDM symbols utilized in a wireless communication system.

II. Background

The introduction of wireless technology for personal communications hasalmost made the traditional telephone a thing of the past. As wirelesstechnologies improve, the sheer numbers of parties desiring tocommunicate wirelessly keep increasing substantially. “Cell” phones havedeveloped into multifunctional devices that not only function to relayvoice communications, but data as well. Some devices have alsoincorporated interfaces to the Internet to allow users to browse theWorld Wide Web and even download/upload files. Thus, the devices havebeen transformed from a simple voice device to a “multimedia” devicethat enables users to receive/transmit not only sound, but alsoimages/video as well. All of these additional types of media havetremendously increased the demand for communication networks thatsupport these media services. The freedom to be ‘connected’ wherever aperson or device happens to be located is extremely attractive and willcontinue to drive future increases in wireless network demand.

Thus, the ‘airwaves’ in which wireless signals are sent becomeincreasingly crowded. Complex signals are employed to utilize signalfrequencies to their fullest extent. However, due to the sheer numbersof communicating entities, it is often not enough to preventinterference of signals. Network identification (ID) is typicallytransmitted with data so that a receiving entity knows the originationof the data. When interferences occur, a receiving entity may not beable to properly interpret what network the signal originated from andmay lose information. This drastically reduces the efficiency of acommunication network, requiring multiple sends of the informationbefore it can be properly received. In the worst case, the data may betotally lost if it cannot be resent. If a network has hundreds or eventhousands of users, the probability of not being able to identify anetwork ID increases substantially. The demand for wirelesscommunications is not decreasing. Therefore, it is reasonable to assumethat signal interferences will continue to increase, degrading theusefulness of existing technology. A communication system that can avoidthis type of data corruption will be able to provide increasedreliability and efficiency to its users.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of some aspects of the embodiments. This summary is not anextensive overview of the embodiments. It is not intended to identifykey/critical elements of the embodiments or to delineate the scope ofthe embodiments. Its sole purpose is to present some concepts of theembodiments in a simplified form as a prelude to the more detaileddescription that is presented later.

The embodiments relate generally to data communications, and moreparticularly to systems and methods for structuring network IDs intoOFDM symbols utilized in a wireless communication system. Multiplenetwork IDs are encoded into symbols utilizing the network IDs as seedsto scramble respective pilots that are then transmitted utilizing thesymbols. The pilots can be structured into a single OFDM symbol and/ormultiple OFDM symbols. The single symbol structure for transmitting thenetwork IDs is independent of the number of network ID bits andminimizes frequency offset and Doppler effects, providing a highspreading gain of network ID data that is highly resistant tointerference from other network ID broadcasts. The multiple symbolstructure, however, allows a much coarser timing accuracy to be employedat the expense of transmitting additional symbols. One embodiment is amethod for facilitating data communications that utilizes at least oneOFDM symbol structured with at least one pilot respective of a networkID for communicating the network ID between entities. Another embodimentis a system that facilitates data communications that includes acommunication component that communicates at least one network IDbetween entities by utilizing at least one OFDM symbol that includes atleast one pilot respective of the network ID.

Several embodiments employ a search function to find possible network IDcandidates from a transmitted symbol and a selection function to find anoptimum candidate from the network ID candidate list. When multiplenetwork IDs are structured into received symbols, typically, a firstnetwork ID is determined and utilized to facilitate in determining asecond network ID. By employing metrics, a score or value can beassigned to each possible ID and an optimum set of network IDs can bedetermined by maximizing the score of the set of IDs. Thus, theembodiments provide a robust, cost-effective means to substantiallyreduce network ID interferences and increase network ID data reception.

To the accomplishment of the foregoing and related ends, certainillustrative embodiments are described herein in connection with thefollowing description and the annexed drawings. These embodiments areindicative, however, of but a few of the various ways in which itsprinciples may be employed and is intended to include all suchembodiments and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a data communication system in accordancewith an embodiment.

FIG. 2 is another block diagram of a data communication system inaccordance with an embodiment.

FIG. 3 is an illustration of scrambling pilots for a single network IDin accordance with an embodiment.

FIG. 4 is an illustration of scrambling pilots for multiple network IDsin accordance with an embodiment.

FIG. 5 is an illustration of single OFDM symbol structures in accordancewith an embodiment.

FIG. 6 is an illustration of dual OFDM symbol structures in accordancewith an embodiment.

FIG. 7 is a block diagram of a network ID decoding component inaccordance with an embodiment.

FIG. 8 is a block diagram of a network ID determination component inaccordance with an embodiment.

FIG. 9 is an illustration of a search metric calculation in accordancewith an embodiment.

FIG. 10 is a flow diagram of a method of constructing an OFDM symbolbased on scrambled pilots generated from network IDs in accordance withan embodiment.

FIG. 11 is a flow diagram of a method of selecting network ID candidatesin accordance with an embodiment.

FIG. 12 is another flow diagram of a method of searching for network IDcandidates in accordance with an embodiment.

FIG. 13 is another flow diagram of a method of selecting network IDcandidates in accordance with an embodiment.

FIG. 14 is a flow diagram of a method of determining a search metric inaccordance with an embodiment.

FIG. 15 illustrates an example communication system environment in whichthe embodiments can function.

DETAILED DESCRIPTION

The embodiments are now described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the embodiments. It may be evident, however, that theembodiments may be practiced without these specific details. In otherinstances, well-known structures and devices are shown in block diagramform in order to facilitate describing the embodiments. As used in thisapplication, the term “component” is intended to refer to an entity,either hardware, software, a combination of hardware and software, orsoftware in execution. For example, a component may be, but is notlimited to being, a processor, a process running on a processor, and/ora multiplexer and/or other signal facilitating devices and software.

In accordance with the embodiments and corresponding disclosure thereof,various aspects are described in connection with a subscriber station. Asubscriber station can also be called a system, a subscriber unit,mobile station, mobile, remote station, access point, base station,remote terminal, access terminal, user terminal, user agent, or userequipment. A subscriber station may be a wireless telephone, a cordlesstelephone, a Session Initiation Protocol (SIP) phone, a wireless localloop (WLL) station, a personal digital assistant (PDA), a handhelddevice having wireless connection capability, or other processing deviceconnected to a wireless modem.

The embodiments provide systems and methods to facilitate communicationof network IDs in wireless systems. Utilization of OFDM symbols providesa means to transmit and receive pilots that have been scrambled basedupon a respective network ID. By decoding the scrambled pilots, thenetwork IDs can be retrieved. In this manner, dedicated symbols canprovide a robust mechanism for relaying network IDs, substantiallyreducing interference from other networks. Additionally, the embodimentsallow for multiple network IDs to be communicated in a single symbol orin multiple symbols. A single symbol structure requires more fine timingaccuracy, while the multiple symbol structure requires coarse timingaccuracy, but at the cost of additional symbols. A typical embodiment ofa multiple structure utilizes separate symbols for each network ID to becommunicated.

Reception and decoding of the network IDs is generally obtainedutilizing a two stage process that includes a search process (that canbe implemented by a search component) for finding a list of possiblenetwork ID candidates and a selection process (that can be implementedby a selection component)for selecting an optimum candidate from thecandidate network ID list. The embodiments provide multiple means fordetermining the network IDs dependent upon the method utilized to encodethe network ID into the symbol(s). Thus, a single symbol that contains atwo network ID structure of interleaved pilots utilizes a differentmethod of decoding than a dual symbol structure that contains a separatesymbol for each network. The selection process itself can be eliminatedby only maintaining a top scored value that is determined by a searchmetric. This essentially reduces a possible network ID candidate list toonly a single choice, negating the necessity of having a follow-onselection process.

Typically, mobile wireless units are not aware of what networks areavailable in a particular area. In order for these units to operate,they must acquire network IDs by intercepting them from wirelesssignals. Normally, there are wide area networks and local area networksin a reception area that each has its own IDs. These IDs act as keys tofacilitate in decoding program material. In a high traffic area,however, it may be difficult for a mobile device to properly interpretnetwork IDs due to interference by other networks in the area.

In FIG. 1, a block diagram of a data communication system 100 inaccordance with an embodiment is shown. The data communication system100 is comprised of an entity “1” 102 and an entity “2” 104. Entity “1”102 and entity “2” 104 each have a communication component 106 and 108respectively. The embodiment is not limited to only two communicatingentities and is shown as such for illustrative purposes only. Entity “1”102 utilizes the communication component 106 to encode its network IDinto an OFDM symbol and transmit it wirelessly. Entity “2” 104 acquiresthe transmitted signal from entity “1” 102 and utilizes itscommunication component 108 to decode the network ID transmitted byentity “1” 102. Once decoded, the network ID can then be utilized tofacilitate in interpreting programming from entity “1” 102. Thetransmitted network ID can be a single OFDM symbol and/or multiple OFDMsymbols. By utilizing the embodiment, the robustness of the acquisitionof the network ID is increased substantially, especially when in a highinterference area. The embodiment also provides a mechanism to transmitmultiple network IDs in a single OFDM symbol and/or multiple OFDMsymbols. This is accomplished by interleaving pilots representative ofthe network IDs in one OFDM symbol and/or utilizing one OFDM symbol perpilot. Additionally, one skilled in the art can appreciate that acommunication component of the embodiments is not required to residewithin a transmitting and/or receiving entity. It can provide the OFDMsymbol structures and/or symbol structure interpretation for thetransmitting and/or receiving component respectively from an external,remote location.

In some communication systems, for example, two layers of network IDsexist such as, for example, network ID type A and network ID type B.Typically, a wireless system needs to acquire network ID type A todecode type A program material and needs to acquire both network ID typeA and network ID type B to decode type B programs. Thus, a system thatdesires, for example, to decode local programming needs to acquire botha wide area programming network ID and a local programming network ID todecode the local programming, while only the wide area programmingnetwork ID is necessary to decode the wide area programming.

Turning to FIG. 2, another block diagram of a data communication system200 in accordance with an embodiment is illustrated. The communicationsystem 200 is comprised of a communication component 202. Thecommunication component 202 is comprised of a network ID encodingcomponent 204 and a network ID decoding component 206. The network IDencoding component 204 receives network “A” ID 208 and network “B” ID210 and encodes the IDs 208, 210 into OFDM symbol(s) 212. The encodingutilizes pilots that are scrambled based on network IDs and insertedinto OFDM symbol(s). This aspect is described in greater detail herein.Once the OFDM symbol(s) have been constructed they are typicallytransmitted for reception by various entities such as, for example,mobile wireless devices. The network ID decoding component 206 receivesOFDM symbol(s) 214 and decodes the symbol(s) into network “A” ID 216 andnetwork “B” ID 218. Once the network IDs are known, a mobile device canutilize them to facilitate in utilizing programming from the respectivenetworks. One skilled in the art will appreciate that the embodimentscan utilize a communication component 202 that has only either a networkID encoding component 204 or a network ID decoding component 206, butnot both. Thus, a wireless device that is utilized to receiveinformation may not have an encoding component 204. Likewise, a networktransmitting device may not have a decoding component 206.

Looking at FIG. 3, an illustration 300 of scrambling pilots for a singlenetwork ID in accordance with an embodiment is shown. In one embodiment,a pseudo-noise sequencer 302 is utilized to facilitate in encoding anetwork ID into an OFDM symbol. The pseudo-noise sequencer 302 receivespilots 304 and employs a network “A” ID as a seed to scramble the pilots304. This creates network “A” ID pilots 308 that contain network IDinformation for network “A.” In FIG. 4, an illustration 400 ofscrambling pilots for multiple network IDs in accordance with anembodiment is depicted. In this embodiment, a pseudo-noise sequencer 402receives pilots 404 and employs both network “A” ID 406 and network “B”ID 408 as seeds to scramble the pilots 404. This produces network “B” IDpilots 410 that contain network ID information for both network “A” andnetwork “B.” Thus, network “A” ID is typically required to be knownbefore the network “B” ID can be decoded. For this reason, a decodingprocess typically decodes the network “A” ID first before decoding thenetwork “B” ID.

The embodiments utilize dedicated OFDM symbols for network IDs. Apreferred embodiment is illustrated in FIGS. 5-6. In this preferredembodiment, the sub-carrier groups are structured as interlaces. Thatis, the sub-carriers of an OFDM symbol is sub-divided into I interlacesindexed from 0 to I−1. Each interlace consists of P sub-carriers wherethe sub-carriers are spaced I×Δf apart in frequency, with Δf being thesub-carrier spacing.

In FIG. 5, an illustration of single OFDM symbol structures 500 inaccordance with an embodiment is shown. In FIG. 5A, one OFDM symbol 502is utilized to transmit both network “A” and network “B” ID informationthrough respective network ID pilots that are interlaced in the symbol.In this embodiment, L(I/L=2,4, . . . , I/2) evenly spaced interlaces arefilled with pilots of which L/2 evenly spaced interlaces are utilizedfor Network “A” and another L/2 evenly spaced interlaces are utilizedfor Network “B,” and the unused interlaces are nulled (no energy). Inthis example, I=8, P=512, and the total number of sub-carriers is,therefore, 4096. In one embodiment (FIG. 5A), L=I=8, four eveninterlaces (0,2,4,6) are utilized for network “A” which are filled withnetwork “A” ID pilots (pilots scrambled by pseudo-noise sequences seededwith network “A” ID). Four odd interlaces (1,3,5,7) are utilized bynetwork “B” and are occupied by network “B” ID pilots (pilots scrambledby network “B” sequences (sequences seeded by both network “A” ID andnetwork “B” ID)). In another embodiment (FIG. 5B), L=I/2, interlaces(0,4) are utilized for network “A” and interlaces (2,6) are utilized bynetwork “B” in one OFDM symbol 504.

Turning to FIG. 6, an illustration of dual OFDM symbol structures 600 inaccordance with an embodiment is shown. In FIG. 6A, network “A” IDpilots are inserted in a single OFDM symbol 602 and network “B” pilotsare inserted into a single OFDM symbol 604. For this dual symbolstructure, the utilized interlaces, L (I/L=1,2, . . . ,I), are evenlyspaced network “A” ID and network “B” ID pilot interlaces inserted inthe network “A” 602 and network “B” 604 symbols, respectively, each ofwhich generates I/L periods in the time domain. In FIG. 6B, anotherembodiment of a dual structure is illustrated where network “A” symbol606 and network “B” symbol 608 are constructed utilizing L=I/4. SingleOFDM symbol structures as shown in FIGS. 5A and 5B utilize less OFDMsymbols but require finer timing. While dual symbol structures as shownin FIGS. 6A and 6B utilize more OFDM symbols but require less accuratetiming, and the required accuracy decreases as L decreases since therepeated number of periods increases. In a general sense, the pilots arescalable. This can be accomplished by increasing the alternatinginterval in a single symbol-based system. Thus, the interval can beevery other one or every other two or every other three, etc. The numberof pilots should be divisible into the total number of frequencyinterlaces to afford a periodic signal that can be easily intercepted atfrequent time intervals.

Once network ID information has been encoded into an OFDM structure, itcan be transmitted to a wireless device. The wireless device thendecodes the symbol structure to determine the network ID(s). Turning toFIG. 7, a block diagram of a network ID decoding component 700 inaccordance with an embodiment is depicted. The network ID decodingcomponent 700 is comprised of a network ID determination component 702.The component 702 receives a signal input 704 and determines a networkID 706 from the signal input 704. The embodiments typically utilize atwo step process to make the network ID determination. Additionally, theprocesses themselves are based upon whether the symbol structureemployed is a single symbol structure or a multiple symbol structure.

In FIG. 8, a block diagram of a network ID determination component 800in accordance with an embodiment is illustrated. The network IDdetermination component 800 is comprised of a search process component802 and a selection process component 804. The search process component802 receives a signal input 806 that contains a network ID encodedwithin an OFDM symbol structure. The search process component 802employs a hypothesis network ID 808 and a search metric 810 tofacilitate in determining a network ID list of possible candidates. Thehypothesis network ID 808 originates from a group of possible networkIDs. The search metric 810 is described in detail herein and establishesa ‘score’ for a particular network ID candidate. The selection processcomponent 804 receives the network ID candidate list and employs aselection metric 812 to facilitate in determining an optimum network ID814. In some embodiments, the selection process component 804 can beomitted.

The acquisition embodiment is utilized to receive the symbol structure502, 504 in FIGS. 5A and 5B and/or 602, 604 and 606, 608 depicted inFIGS. 6A and 6B. After timing is established, network “A” ID symbol issampled one or multiple periods depending on the timing accuracy andtransformed into the frequency domain. The “L_(A) ^(”) number of network“A” ID pilot interlaces are descrambled utilizing one of the hypothesisnetwork “A” IDs and IFFT (Inverse direct Fast Fourier Transform)transformed to obtain an L*512-tap time-domain channel observation. Thenetwork “A” ID search metric is calculated and added to a candidate set,A_(M), of size M, if it makes it to the top M. This process continuesuntil all of the network “A” ID hypotheses are tested.

The network “B” ID symbol is then sampled one or multiple periods. TheL_(B) interlaces are descrambled utilizing one of the hypothesis network“B” IDs combined with a network “A” ID in the network “A” candidate set,A_(M). The network “B” search metric is then calculated and added to thenetwork “B” candidate set, B_(N), of size N, if it makes it to the topN. This process continues until all the network “A” IDs in the network“A” candidate set are combined with all the network “B” ID hypothesesand tested.

After the network “A” ID/network “B” ID candidate search processfinishes, a selection process begins. The selection process isadditionally beneficial in terms of time diversity since the search datais from a fraction of one OFDM symbol. Increased time diversityfacilitates to make a better selection from a candidate set. Theselection metric is calculated for all the candidates from the nextnetwork ID symbols. The selection metric, a combination of searchmetrics from different network ID symbols, therefore, provides more timediversity than the search metric does. The network “A” ID with the bestselection metric is selected as the optimum network ID candidate. Thenetwork “B” ID is selected from network “A”/network “B” ID combinationsthat yield the best selection metric score. The design of the selectionmetric is discussed herein. In one embodiment, the selection process canbe avoided by setting M=N=1.

An optimum network “A”/network “B” ID combination is the one with thelargest combined search metric:

$\begin{matrix}{\left( {{NETA},{NETB}} \right)^{*} = {\max\limits_{{{NETA} \subseteq A_{M}},{{NETB} \subseteq B_{N}}}{\left\{ {{\sum\limits_{s = 1}^{S}\;{\eta_{NETA}(s)}} + {\eta_{{NETA},{NETB}}(s)}} \right\}.}}} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$where S is the number of time diversity combinations from the selectionprocess.

In FIG. 9, an illustration 900 of a search metric calculation inaccordance with an embodiment is shown. When pilot samples are muchlonger than a maximum channel, e.g., L=4, the network “A”/network “B”search metric is calculated utilizing the following procedure. 512L tapnetwork “A”/network “B” time-domain channel observations are divided,for example, into 16 bins 902, each of which is 128 taps long. Bins 0-5904 are utilized for channel activity detection (assuming, for example,that a channel spread is less than 768 taps). Bins 7-14 906 are utilizedfor noise baseline/interference power spectral density (PSD)calculations since no channel activity should exist in this zone. Toallow possible channel energy leakage from the channel activity zone 904into noise baseline detection zone 906 due to miss-time alignment, Bin 6908 and Bin 15 910 are not utilized for the interference PSDcalculation.

The search metric for the nth TDM pilot network “A”/network “B” symbolis defined as follows for the detected PSD energy, η 916:

$\begin{matrix}{{{{\eta^{(i)}(n)} = {\sum\limits_{k = 0}^{{5 \cdot 128} - 1}\;\left( {\max\left\{ {{{s_{k}^{(i)}(n)} - {\lambda\;{w^{(i)}(n)}}},0} \right\}} \right)}};}{{where}\text{:}}{{{w^{(i)}(n)} = {\frac{1}{8 \cdot 128}{\sum\limits_{k = {7 \cdot 128}}^{{14 \cdot 128} - 1}s_{k}^{(i)}}}};}} & \left( {{Eq}.\mspace{14mu} 2} \right)\end{matrix}$is the interference PSD energy 912, s_(k) ^((i)) is the energy 914 ofthe kth sample under the ith hypothesis and λ is a predeterminedconstant. The search metric is an unbiased estimate of the total energyof the channel under the hypothesis.

The final search metric with S selection diversity is:

${\eta^{(i)} = {\sum\limits_{s = 1}^{S}\;{\eta^{(i)}(s)}}};$which is the sum of the search metric obtained from both network“A”/network “B” ID symbols to gain time-diversity as well as reduceestimation variance. This search metric does not assume any channelprofile and, therefore, is channel profile safe.

In the case of a mismatch between a hypothesis ID and a correct ID, thechannel energy of the correct ID broadcast will be evenly spread overthe whole 16 bins, and no significant channel energy should be detectedin the activity zone utilizing the search metric, i.e., η→0. However, ifthe hypothesis ID matches the correct ID, the broadcast channel with thecorrect ID will be dispread, and the channel energy will be confinedwithin the activity zone. For channels who's ID does not match ahypothesis ID, the channel energy will be spread over the whole 16 bins.In this case, significant energy will be detected utilizing the searchmetric, i.e., η□ 0.

However, in the case where the pilot samples are not longer than amaximum channel, such as I=1 in FIG. 6, a separation between the channelunder hypothesis and interference does not exist. The channel activityzone and the noise zone overlaps. Therefore, the interference PSD, w, in(Eq. 2) is a biased estimate (over-estimate) of the interference PSD. Inthe extreme case when L=1 and the channel is longer than 512, theinterference PSD estimate becomes:

$\begin{matrix}{{w = {\frac{1}{4 \cdot 128}{\sum\limits_{j = 0}^{{4 \cdot 128} - 1}\; s_{j}}}};} & \left( {{Eq}.\mspace{14mu} 4} \right)\end{matrix}$which is always an over-estimate of the interference power spectraldensity. The search metric defined in (Eq. 2) then becomes:

$\begin{matrix}{{{\overset{\sim}{\eta}}^{(i)} = {\sum\limits_{k = 0}^{{4 \cdot 128} - 1}{\max\left\{ {\left( {s_{k}^{(i)} - {\lambda\; w}} \right),0} \right\}}}};} & \left( {{Eq}.\mspace{14mu} 5} \right)\end{matrix}$resulting in a biased estimate (under-estimate) of the energy of thechannel under hypothesis. The flatter the channel time response, thegreater the bias. In other words, unlike the search metric in (Eq. 2)which is profile independent, the search metric in (Eq. 5) favors thechannel with a concentrated profile, although an OFDM receiver ingeneral does not have this discrimination.

In view of the exemplary systems shown and described above,methodologies that may be implemented in accordance with the embodimentswill be better appreciated with reference to the flow charts of FIGS.10-14. While, for purposes of simplicity of explanation, themethodologies are shown and described as a series of blocks, it is to beunderstood and appreciated that the embodiments are not limited by theorder of the blocks, as some blocks may, in accordance with theembodiments, occur in different orders and/or concurrently with otherblocks from that shown and described herein. Moreover, not allillustrated blocks may be required to implement the methodologies inaccordance with the embodiments.

In FIG. 10, a flow diagram of a method 1000 of constructing an OFDMsymbol based on scrambled pilots generated from network IDs inaccordance with an embodiment is shown. The method 1000 starts 1002 byobtaining a network ID for network “A” 1004 and network “B” 1006. Thesenetworks can be a wide area network and a local area network and thelike. Typically, utilization of the local area network programmingrequires both the local area ID and the wide area ID. A first set ofpilots are then scrambled with a pseudo-noise sequencer seeded bynetwork “A” ID 1008. This encodes the network ID into the pilots. Asecond set of pilots are then also scrambled with a pseudo-noisesequencer seeded by both network “A” ID and network “B” ID 1010. Thisencodes the network “B” ID into the scrambled pilots, but also requiresthat network “A” ID be known to facilitate in decoding the network IDs.OFDM symbol(s) are then constructed utilizing both sets of scrambledpilots 1012, ending the flow 1014. The pilot sets can be interleaved ina single OFDM symbol and/or one OFDM symbol can be employed for each setof pilots. Utilizing a single OFDM symbol requires higher accuracy intiming for acquisition than with multiple symbols.

Turning to FIG. 11, a flow diagram of a method 1100 of selecting networkID candidates in accordance with an embodiment s illustrated. Thismethod 1100 of selecting an optimum network ID candidate is typicallyemployed with transmission of network IDs utilizing a single OFDMsymbol. The method 1100 starts 1102 by obtaining a network ID candidatelist 1104. The network ID candidate list is typically constructed asdescribed herein. A selection metric value or score is then determinedfor each candidate 1106. The selection metric is calculated for allcandidates from the pilot symbols at the boundaries of frames of thesuperframe. It provides more time diversity than the search metric. Anoptimum candidate is then selected based on the selection metricvalues/scores 1108, ending the flow 1110.

Looking at FIG. 12, another flow diagram of a method 1200 of searchingfor network ID candidates in accordance with an embodiment is shown.This method 1200 is generally applicable to network IDs transmittedutilizing a multiple OFDM symbols. The method 1200 starts 1202 byacquiring an input signal 1204 and establishing the SFN timing 1206. Anetwork ID pilot is then sampled 1208 and transformed into the frequencydomain 1210. A hypothesis network ID is utilized to facilitate indescrambling the pilot interlaces which are then employed to obtain atime-domain channel observation 1212. A network ID search metric is thencalculated 1214 and utilized to construct a network ID candidate list1216, ending the flow 1218.

Moving on to FIG. 13, another flow diagram of a method 1300 of selectingnetwork ID candidates in accordance with an embodiment is depicted. Thismethod 1300 selects an optimum combination of network IDs and can beapplicable to either single OFDM symbol construction and/or multiplesymbol construction network ID transmission acquisitions. The method1300 starts 1302 by obtaining a network ID candidate list for network“A” 1304 and a network ID candidate list for network “B” 1306. Thecandidate list can be obtained according to the flow in FIG. 12. Anoptimum combination of network ID “A” and network ID “B” is thendetermined based on search metric scores 1308, ending the flow 1310.When determining an optimum second network ID from a candidate list, thesecond network ID is selected from the highest scoring combination ofthe first and second network IDs after the first optimum network ID hasbeen determined.

In FIG. 14, a flow diagram of a method 1400 of determining a searchmetric in accordance with an embodiment is shown. The search metric canbe applicable to both single and multiple OFDM symbol network IDtransmissions. The method 1400 starts 1402 by determining if pilotsamples are longer than a maximum channel 1404. If yes, network IDtime-domain channel observations are divided into “X” bins that are “Y”taps long, where X and Y are integers from one to infinity 1406. A firstsubset of the bins is utilized for detecting channel energy in the formof power spectral density (PSD) energy 1408. A second subset of binsseparated by guard zones is utilized to determine a noise baseline orinterference PSD energy 1410. Channel energy (detected PSD) is thendetermined by eliminating the interference PDS energy from the obtainedPSD energy 1412, ending the flow 1414. When a mismatch occurs between ahypothesis network ID and a correct network ID, the channel energy ofthe correct network ID is broadcast evenly over all of the bins and,therefore, no significant amount of energy is detected in the firstsubset of bins. However, if a match occurs, the broadcast channel withthe correct network ID is dispread, and the channel energy is confinedwithin the first subset of bins. This form of the search metric providesan unbiased estimate of the total energy of the channel underhypothesis. Examples of this process are described herein and areillustrated in FIG. 9.

If, however, the pilot samples are not longer than the maximum channel1404, the channel energy is determined by eliminating an average PSDenergy from the obtained PSD energy 1416, ending the flow 1414. Theaverage PSD energy is utilized in this instance because no separationbetween the channel under hypothesis and the interference PSD exists.Utilizing the average PSD energy generally produces an over-estimate ofthe interference PSD resulting in a biased estimate of the channel underhypothesis.

FIG. 15 is a block diagram of a sample communication system environment1500 with which the embodiments can interact. The system 1500 furtherillustrates two representative communication systems A 1502 and B 1504.One possible communication between systems A 1502 and B 1504 may be inthe form of a data packet adapted to be transmitted between two or morecommunication systems. The system 1500 includes a communicationframework 1506 that can be employed to facilitate communications betweenthe communication system A 1502 and communication system B 1504.

In one embodiment, a data packet transmitted between two or morecommunication system components that facilitates data communications iscomprised of, at least in part, information relating to a network IDthat is communicated with at least one OFDM symbol structure thatemploys at least one pilot respective of the network ID.

What has been described above includes examples of the embodiments. Itis, of course, not possible to describe every conceivable combination ofcomponents or methodologies for purposes of describing the embodiments,but one of ordinary skill in the art may recognize that many furthercombinations and permutations of the embodiments are possible.Accordingly, the embodiments are intended to embrace all suchalterations, modifications and variations that fall within the spiritand scope of the appended claims. Furthermore, to the extent that theterm “includes” is used in either the detailed description or theclaims, such term is intended to be inclusive in a manner similar to theterm “comprising” as “comprising” is interpreted when employed as atransitional word in a claim.

The invention claimed is:
 1. A method for facilitating datacommunications, comprising: utilizing at least one orthogonalfrequency-division multiplexing (OFDM) symbol structured with at leastone pilot respective of a network identification (ID) for communicatingthe network ID between entities; calculating a search metric, whereinthe search metric comprises an unbiased estimate of total channel energyderived from the pilot; employing, by a receiving entity, a searchprocess using the search metric to determine network ID candidates basedon the calculated search metric; calculating a selection metric for eachnetwork ID candidate, each selection metric having a value; and,employing a selection process to determine at least one optimum networkID candidate based on the values of the selection metrics.
 2. The methodof claim 1 further comprising: employing an OFDM symbol structure withone pilot respective of the network ID per OFDM symbol.
 3. The method ofclaim 1 further comprising: employing an OFDM symbol structure withpilots respective of the network ID interleaved in at least one OFDMsymbol.
 4. The method of claim 1, the entities comprising networksand/or mobile devices.
 5. The method of claim 1 further comprising:constructing the at least one OFDM symbol through utilization of thenetwork ID to facilitate in scrambling the pilot respective of thenetwork ID, the pilot being utilized in the at least one OFDM symbol. 6.The method of claim 5 further comprising: employing a pseudo-noise (PN)sequence generator, seeded by at least one network ID, to facilitate inscrambling the pilot respective of the network ID.
 7. The method ofclaim 1, the search metric comprising a metric of an unbiased estimateof total energy, η, of a channel based on${{\eta^{(i)}(n)} = {\sum\limits_{k = 0}^{{5 \cdot 128} - 1}\left( {\max\left\{ {{{s_{k}^{(i)}(n)} - {\lambda\;{w^{(i)}(n)}}},0} \right\}} \right)}};$where n is the nth pilot symbol,${w^{(i)}(n)} = {\frac{1}{8 \cdot 128}{\sum\limits_{k = {7 \cdot 128}}^{{14 \cdot 128} - 1}s_{k}^{(i)}}}$ is an interference power spectral density (PSD) energy, and s_(k)^((i))is an energy of a kth sample under an ith hypothesis, and λ is apredetermined constant.
 8. The method of claim 7, the search metric withS selection diversity for an interleaved network ID pilot symbolcomprising: $\eta^{(i)} = {\sum\limits_{s = 1}^{S}\;{{\eta^{(i)}(s)}.}}$9. The method of claim 1, the search process comprising: determining atleast one candidate network ID list of the network ID candidates;determining at least one network ID candidate set from the network IDcandidate list according to the search metric; and determining at leastone of a top candidate list from a candidate set A_(M) for a firstnetwork ID type and at least one a top candidate list from a candidateset B_(N) for a second network ID type based on the determination of theat least one network ID candidate set.
 10. The method of claim 1, theselection process comprising: determining the selection metric for thenetwork ID candidates; and determining the optimum network ID from atleast one network ID candidate list of the network ID candidates basedon the selection metric.
 11. The method of claim 10 further comprising:determining an optimum combination of the network ID candidates from theat least one candidate network ID list to facilitate in determining aplurality of network IDs.
 12. The method of claim 11, the optimumcombination comprising a maximized value of search metrics based on:${\left( {{NETA},{NETB}} \right)^{*} = {\max\limits_{{{NETA} \subseteq A_{M}},{{NETB} \subseteq B_{N}}}\left\{ {{\sum\limits_{s = 1}^{S}\;{\eta_{NETA}(s)}} + {\eta_{{NETA},{NETB}}(s)}} \right\}}};$where NETA represents a first network ID, NETB represents a secondnetwork ID, A_(M) is a first network ID candidate set of size M, B_(N)is a second network ID candidate set of size N, η is a value of a searchmetric, and S is a number of time diversity combinations from aselection process.
 13. The method of claim 1, the network ID comprisinga wide area network ID and/or a local area network ID.
 14. The method ofclaim 13 further comprising: employing the at least one OFDM symbol witha local area network ID pilot scrambled utilizing both the local areanetwork ID and the wide area network ID.
 15. A system that facilitatesdata communications, comprising: a communication component thatcommunicates at least one network identification (ID) between entitiesby utilizing at least one orthogonal frequency-division multiplexing(OFDM) symbol that includes at least one pilot respective of the networkID; a calculation component configured to calculate a search metric,wherein the search metric comprises an unbiased estimate of totalchannel energy derived from the pilot; a search component configured toemploy a search process using the search metric to determine network IDcandidates based on the calculated search metric; a selection metriccalculation component configured to calculate a selection metric foreach network ID candidate, each selection metric having a value; and aselection component configured to employ a selection process todetermine at least one optimum network ID candidate based on the valuesof the selection metrics.
 16. The system of claim 15, wherein thecommunication component is configured to employ one OFDM symbol for onepilot respective of the network ID.
 17. The system of claim 15, whereinthe communication component is configured to interleave respectivenetwork ID pilots in at least one OFDM symbol.
 18. The system of claim15, wherein the communication component is configured to utilize atleast one network ID to facilitate in scrambling the at least one pilotrespective of the network ID, the at least one pilot being employed inthe OFDM symbol.
 19. A method for facilitating data communications,comprising: utilizing at least one orthogonal frequency-divisionmultiplexing (OFDM) symbol structured with at least one pilot respectiveof a network identification (ID) for communicating the network IDbetween entities; employing, by a receiving entity, a search process todetermine network ID candidates based on a search metric; wherein thesearch process utilizes a hypothesis network ID to facilitate in thesearch process and wherein the search metric comprises a metric of anunbiased estimate of total energy of a channel; and employing aselection process using a selection metric generated for each network IDcandidate to select at least one optimum network ID candidate.
 20. Asystem that facilitates data communications, comprising: a communicationcomponent that communicates at least one network identification (ID)between entities by utilizing at least one orthogonal frequency-divisionmultiplexing (OFDM) symbol that includes at least one pilot respectiveof the network ID; a search component configured to employ a searchprocess to determine network ID candidates based on a search metric,wherein the search process utilizes a hypothesis network ID tofacilitate in the search process and wherein the search metric comprisesa metric of an unbiased estimate of total energy of a channel; and aselection component configured to employ a selection process todetermine at least one optimum network ID candidate by utilizing aselection metric generated for each network ID candidate.
 21. The systemof claim 20 wherein the hypothesis network ID originates from a group ofpossible network IDs.
 22. A non-transitory computer readable mediumstoring computer executable code for facilitating data communications,comprising code for: utilizing at least one orthogonalfrequency-division multiplexing (OFDM) symbol structured with at leastone pilot respective of a network identification (ID) for communicatingthe network ID between entities; calculating a search metric, whereinthe search metric comprises an unbiased estimate of total channel energyderived from the pilot; employing, by a receiving entity, a searchprocess using the search metric to determine network ID candidates basedon the calculated search metric; calculating a selection metric for eachnetwork ID candidate, each selection metric having a value; andemploying a selection process to determine at least one optimum networkID candidate based on the values of the selection metrics.
 23. Thenon-transitory computer readable medium of claim 22 further comprisingemploying an OFDM symbol structure with one pilot respective of thenetwork ID per OFDM symbol.
 24. The non-transitory computer readablemedium of claim 22 further comprising further comprising employing anOFDM symbol structure with pilots respective of the network IDinterleaved in at least one OFDM symbol.
 25. The non-transitory computerreadable medium of claim 22, the entities comprising networks and/ormobile devices.
 26. A non-transitory computer readable medium storingcomputer executable code for facilitating data communications,comprising code for: utilizing at least one orthogonalfrequency-division multiplexing (OFDM) symbol structured with at leastone pilot respective of a network identification (ID) for communicatingthe network ID between entities; employing, by a receiving entity, asearch process to determine network ID candidates based on a searchmetric; wherein the search process utilizes a hypothesis network ID tofacilitate in the search process and wherein the search metric comprisesa metric of an unbiased estimate of total energy of a channel; andemploying a selection process using a selection metric generated foreach network ID candidate to select at least one optimum network IDcandidate.